Why is my AC making a hissing noise?

July 25, 2019

A hissing noise coming from your HVAC system should not be disregarded. Among the possible causes are leaky refrigerant lines, an internal valve leak or a serious failure with your compressor. If the hissing noise is originating from your ductwork, then you could have leaking air ducts. This is annoying, but not necessarily a cause for alarm. A hissing sound may be a sign for any of these things, but we’ll try to narrow it down a little further.

Does the hissing sound stop after a few seconds?

If you hear a hissing noise that stops after a few moments, you may not have any problems. That can be refrigerant in your expansion valve, which is a part of the normal operation of your HVAC unit.

Is the AC Making a Hissing Sound with Bubbling Noises?

Are you hearing a bubbling sound along with a hissing sound? This can indicate a refrigerant leak. If a refrigerant leak develops, you may notice a slight hissing sound as the refrigerant escapes from the leak. It escapes as a gas and can be a worrisome health concern. If you see signs of a refrigerant leak, shut down your HVAC and call a qualified HVAC company to come evaluate the noise.

If the cause is a valve leak, it should be repaired by a technician as soon as possible. The job of the valves is to manage the pressurization of the refrigerant gas and if unresolved, the leak will worsen. When it does, the hissing sound will sometimes grow louder, which can be a sign if you’re looking for a cause. You must maintain proper pressure in your HVAC system for it run as intended, and leaks create additional health and mechanical problems. You want to get this fixed post haste if possible.

Are Hissing Noises Coming from the Compressor?

The compressor can be located in the outdoor air conditioning unit, which is also known as a condenser unit. Listen quietly for the hissing noise. If the compressor is the problem, this could be a dangerous situation because it is a signal that the pressure within the compressor is too much. If you hear hissing, whistling, or shrieking coming from your compressor, shut off your air conditioner without delay and call a professional technician.

AC compressor located in exterior condenser unit 

Compressors are some of the most costly parts to repair or replace inside an AC unit. Compressors are the part responsible for pushing refrigerant through the system. You cannot turn on an air conditioner and cool your home without a compressor. The cost changes based on factors such as the type, unit size, and brand requirements. If you have a two stage compressor in your AC, you would need to replace it with another two stage compressor. It’s impossible to upgrade or downgrade the compressor type - your unit has specific requirements for what components are installed and can’t be MacGyvered. While it’s impossible to provide estimates because of the variable costs, the bill is frequently large enough to just do a replacement in older air conditioners. This is why it’s critical to shut off the air conditioning and call a trustworthy HVAC company if you hear hissing sounds coming from the compressor.

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